Do you have a deduplication server (a media server with msdp pool) with a pool up and running?

If not, you have to build a msdp pool . KEEP THE PASSWORD YOU WILL PUT @ THE POOL SOMEWHERE.You may need it sometime.

If yes, you have to add an entry at the "client attributes" section as stated above at the second post.Then, you will deside which side will do the dedup.Client side is more network free method (especially if you have WAN lines between) but you will also have some CPU overhead.

I am using a Netbackup Enterprise Server 6.5.6, I´ll update to 7.5, soo I have to learn almost everything about Client side deduplication.

Today I have

1 Master/Media server

3 Libraries, SL180, SL24, DL4000

At the master/media server I have set 1TB for disk Staging,

I got perm to upgrade the NBU, as soon as a I can backup clients by WAN (or VPN) some desktops, laptops, and Small Servers. of course I´ll need client side dedup, but I really don´t know where to start.

What is the client side size of the data?
Nature of the data (video,pst's,jpg,db etc)?

Master/media//dedup in the same system is not the optimal solution.You may need to move the media server to a new system (or make a VM master server with enough resources).

You have to find out what size the pool got to have.The pool size is related to the type of the data.For example my databases at 7.1 averages at 65% deduplication rate, which means that you add in the pool the rest 35% of database size at each backup. Don't have 7.5 yet but i read that the feel is similar.

About configure the msdp pool.Have you used dedup at 6.5 ? It is quite similar but it is called MSDP now.Via the console choose the "configure disk storage server" .It will guide you through the MSDP pool config process.KEEP THE CREDENTIALS you use.You may need them at some point....
You may need to go through "configure disk pools" but i think that it is triggered at the above process

Once you are done with it and the pool is visible at "media and device management"-->device--> disk pool you can start thinking about the rest.
Are you going to store the data only at the pool or you will export (rehydrate is the term) the data to some tape (or other disk pool)?
If you will rehydrate , you have to configure a SLP (storage lifecycle policy) ,have a look at the storage.That slp you will use as storage device within policy (or schedule).

Aftewards the rest is easy,go to the master server properties --> client attributes and put the name of t he client and the side which the deduplication takes place.

Have in mind, you have to introduce few clients at each backup session.In that way , those clients will create the hashes which are needed (within the pool) and the rest clients have better chances to have high dedup rate at once.

Have in mind one more thing also.
If you are giong to rehydrate , the storage MUST BE FASTER than 120Mbyte/sec.Anything less and the LTO3(and later) drives will start "shoe shinning".
You have to find out the size of the data.It is essential for the pool size to know that.....